The invention relates generally to resonant sensors, and more particularly to impedance readers for resonant sensors and methods of making such impedance readers.
Generally, RFID readers are used to obtain digital data from RFID tags. Digital data may include, for example, digital identification of the tag, or any other information written and/or stored in a memory chip of the RFID tag. The RFID tags transmit electromagnetic signals at different relative levels of transmitted power at different times. Signals received by the RFID reader in combination with the transmitted relative power level of the received signals are employed to locate the RFID tags, and read the digital identification information from the RFID tag (e.g., from the memory chip or back-reflector structure of the RFID tag).
Resonant sensors are used for sensing physical, chemical, and biological constituents in a sample. Examples of the resonant sensors may include RFID sensors, or LCR sensors, where L stands for inductor, C stands for capacitor, and R stands for resistor. The resonant sensors are cost-effective, and easy to incorporate in a component or a system for measuring physical, chemical or biological constituents of the component or the system.
Typically, analog or sensor data from the resonant sensors, such as the LCR sensors or the RFID sensors, is read using an impedance reader. Typically, passive RFID tags are used to make the RFID sensors because passive RFID tags are cost efficient as compared to active RFID tags. However, with the passive tags, the read range is influenced by frequency, reader output power, antenna design, and method of powering the RFID tags. In lab environment, bulky desktop-based laboratory reader systems are employed that need line power, limiting the applicability of the resonant sensors to lab environment. Hence, applications of such resonant sensors are limited by availability of the readers. Specifically, it may be difficult to provide a reader in field situations, or places outside a lab environment.
Therefore, it is desirable to have a field-portable impedance reader for the resonant sensors.